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Published on: March 15, 2019
Altered C-tactile processing in human dynamic tactile allodynia.
Jaquette Liljencrantz1, Malin Björnsdotter, India Morrison
1Institute of Neuroscience and Physiology, University of Gothenburg, 413 90 Gothenburg, Sweden Alan Edwards Centre for Research on Pain, McGill University, Montreal, Canada Department of Clinical Neurophysiology, Poole Hospital and University of Bournemouth, Bournemouth, UK Department of Integrative Physiology, School of Medicine, University of Western Sydney, Sydney, Australia.
Tactile allodynia, an unpleasant sensation from touch after nerve injury, involves both Aβ and C-tactile afferents. This study found reduced pleasant touch processing in allodynia, but Aβ afferent signaling is crucial for developing this pain.
Area of Science:
- Neuroscience
- Somatosensation
- Pain Research
Background:
- Human unmyelinated (C) tactile afferents normally signal pleasant touch during gentle skin stroking.
- Tactile allodynia, an unpleasant sensation from touch post-neuronal injury, is often explained by Aβ afferent sensitization accessing pain pathways.
- Recent findings suggest C-tactile afferents may also contribute to allodynia development.
Purpose of the Study:
- To investigate the role of C-tactile afferents in human tactile allodynia.
- To differentiate the contributions of Aβ and C-tactile afferents to allodynic sensations.
Main Methods:
- Utilized the heat/capsaicin model of tactile allodynia in 43 healthy subjects.
- Included 2 patients with sensory neuronopathy lacking Aβ afferents for comparison.
- Employed functional magnetic resonance imaging (fMRI) in 18 healthy subjects and 1 patient to assess brain activity.
Main Results:
- Healthy subjects reported tactile-evoked pain, while patients lacking Aβ afferents did not.
- Patients reported a significantly weaker pleasant touch (C-touch) percept in the allodynic zone.
- fMRI revealed distinct cortical responses in the posterior insular cortex and reduced medial prefrontal cortex activation in allodynic conditions.
Conclusions:
- Dynamic tactile allodynia is associated with diminished C-tactile mediated hedonic touch processing.
- Aβ afferent signaling appears essential for the development of tactile allodynia under these experimental conditions.
- Both Aβ and C-tactile afferent pathways are implicated in the complex sensory changes observed in tactile allodynia.
